JPH07502199A - Method for bubble-free introduction of hydrogen into aqueous liquid - Google Patents

Abstract

PCT No. PCT/EP92/02924 Sec. 371 Date Jun. 20, 1994 Sec. 102(e) Date Jun. 20, 1994 PCT Filed Dec. 16, 1992 PCT Pub. No. WO93/13022 PCT Pub. Date Jul. 8, 1993.The invention relates to a method of introducing hydrogen into aqueous liquids without forming bubbles. In this case, the introduction of the gas takes place through a composite membrane with a non-porous coating on the liquid side. Preferred fields of use relate to the charging of hydrogen into biologically or catalytically operating processes for the removal of oxygen, nitrite and/or nitrate from water.

Description

[Detailed description of the invention] A method for introducing hydrogen into an aqueous liquid without bubbles The present invention provides a method for introducing hydrogen into an aqueous liquid through a membrane. This invention relates to a method for bubble-free delivery of .

In a series of chemical, biological, biochemical and other industrial processes, e.g. In the case of biological or catalytically promoted reductions of substances with hydrogen, even if For biological or catalytic reduction of oxygen, nitrite or nitrate in water, It is necessary to pump hydrogen into an aqueous liquid.

In general, hydrogen can be introduced bubble-wise or bubble-free. air Foam gas treatment is actually very simple to implement, but is inefficient. On the other hand , bubble-free gas delivery allows better utilization of the gas to be delivered. nitrite and/or selective nitrification of these health-hazardous components into water containing nitrates. Bubble-free introduction of hydrogen through the membrane for catalytic removal during elementary formation is It is known from European Patent (EP-A) No. 359074. recognized as advantageous Bubble-free delivery of contained gases is possible through non-porous, unreinforced or woven materials. This is done via reinforced silicone hoses or silicone flat membranes.

These silicone hoses have a low mechanical load capacity despite their large wall thickness .

German Patent Application No. 3544382 (DE-O8) describes a bioreactor The method of oxygen consumption and the equipment that can be used for it are described. Hydrogen is bubble-free into the aqueous phase through a silicone membrane with textile reinforcement, without pores. . Therefore, silicone hoses described as “thin wall” have a thickness of 0.2 to 0.5 mm. It has a wall thickness of . Although the amount of gas transported is small, there is a high risk of forming bubbles. . The amount of gas dissolved in water is also minimal.

It is an object of the present invention to provide an improved method for bubble-free introduction of hydrogen into aqueous liquids. Ru. This object is solved by the method according to the invention as defined in the claims.

A book on introducing hydrogen into an aqueous liquid through a membrane, and introducing hydrogen into an aqueous liquid without bubbles. The inventive method comprises: a) a carrier structure formed from a porous polymer; and b) a non-porous porous polymer. A membrane containing at least one layer of reamer is used, with no aqueous liquid being present. It is characterized in that it is in contact with the membrane on the side of the layer consisting of porous polymer.

Composite membranes with assembled asymmetric structures are particularly suitable. The composite membrane is made of porous polymer and includes a carrier structure having a microporous layer and a non-porous coating. Kaka The membrane and its manufacture are described in European Patent (EP-A) No. 291,679 (US- A No. 4933085).

The carrier structure with a microporous layer is usually produced in one step and consists of a hydrophobic water-resistant porous layer. remers, such as polysulfones, such as polyethersulfones, polyamides, It is formed from polyimide or especially polyetherimide.

The assembled asymmetric composite membrane used in the method of the invention has the following structure: One side of the membrane is formed by a non-porous layer of hydrophobic polymer. other side of membrane This is usually followed by a microporous film. ruktur") or void-free spongy structures. Cavity-containing structures are The spongy structure is more or less variable depending on the desired stability of the membrane. do. Advantageously, the thickness is in the range from 15 to 200 μm.

Typically, the microporous layer is overlaid with a hydrophobic, nonporous polymer. For example, polymethyl Layers consisting of pentene and silicone polymers, especially polydialkylsiloxanes A layer of, for example, polydimethylsiloxane is suitable. The thickness of this non-porous layer The diameter is between 01 and 100 μm, particularly between 0.5 and 10 μm. unless you can buy it The production of assembled asymmetric membranes and composite membranes is described, for example, in European patents (EP-A). No. 291679.

The membrane can be used as a flat membrane, a tubular membrane (diameter 4-15 mm or more) or in particular It may be configured as a hollow fiber membrane.

If hollow fiber membranes are used in the process according to the invention, the internal diameter is preferably between 0.2 and 4 m. It is within the range of m.

The length dimensions of the assembled asymmetric membrane can be varied as desired. A large number of individual membranes It can be arranged in modules or cassettes.

It has already been mentioned that the aqueous liquid is brought into contact with the membrane on the side of the non-porous membrane. In this case, advantageously Pass the liquid past the layer. This is particularly preferably carried out in turbulent flow. Also inside As long as hollow fiber membranes are used, is the non-porous layer placed inside the hollow fibers (in this case The hydrophilic liquid may flow through the hollow fibers) or be located outside the hollow fibers ( In this case, the aqueous liquid washes around the hollow fibers). Of course, with a non-porous layer on both sides Membranes can also be used. Preferably, a non-porous layer is arranged on the inside; Hollow fiber membranes are used in which the aqueous liquid flows through the cavities of the threads. Advantageously turbulent conditions will be accomplished.

Gas delivery rate depends on various factors. The driving forces behind the movement of gas into the aqueous phase The power is the partial pressure gradient of the gas to be introduced between the gas phase and the aqueous phase. on the gas side The higher the differential pressure, the higher the gas delivery rate.However, if the differential pressure is too high, In some cases, the membrane may be damaged and further unwanted bubble formation may occur. . For this purpose, it is advantageous to work below the pressure at which undesired bubble formation begins. water The elementary pressure must be higher than the partial pressure of hydrogen in water. Advantageously hydrogen gas The pressure difference between and water is less than 10 bar. If desired, add it to an aqueous liquid. A preload is applied for a moment before it contacts the membrane. This allows the gas to be introduced to dissolve. degree is improved.

Gas treatmentThe formation of undesirable bubbles in one culm requires the sum of the partial pressures of gas dissolved in water. Since the Advantageously, it is removed by means of sorbents or adsorbents.

Evacuation of gases dissolved in water also takes place through the membrane used. Membrane for gas discharge is controlled by the permeability of the gas, where the partial pressure gradient of the gas between the aqueous phase and the gaseous membrane is Acts as a propulsive force. The very thin non-porous layer of the composite membrane used has a very advantageous effect. produce fruit. That is, undesirable gases introduced from the water into the gas space cause water The concentration or partial pressure of the hydrogen to be introduced therein is reduced.

However, the small amount of gas expelled from the water has little effect. gas space body If a large amount of gas is carried into this gas space from the aqueous medium in proportion to the The effect of this is to remove the gas entering the gas space through the membrane by continuous or intermittent cleaning. It can be restricted by Each gas type (mainly oxygen, nitrogen) It is also possible to place adsorbent materials in the gas space that are suitable for Ru. Water vapor that may permeate the membrane can likewise be removed by washing or adsorption. I can do it.

In particular, in the method of the present invention for introducing hydrogen, hydrogen is used as an electron donor or as a reducing agent. Combined with the method of working as. This can be for example catalyzed or non-catalyzed It may be a scientific or biological method. It is particularly desirable to introduce hydrogen into The method of the present invention, in which the oxygen content, nitrite content and/or nitrate content is determined using hydrogen. biologically or catalytically reduced, e.g. within the framework of autotrophic denitrification. It is a combination of methods.

Oxygen-poor water is required, for example, to reduce corrosion. In other scopes of application However, oxygen-poor water is required, for example in the beverage industry. Contains nitrite The amount or nitrate content can be determined in various forms (groundwater, drinking water, beverage and food production). (as water) is undesirable in the water supply necessary for human life. industrial water or It is also desirable to reduce the nitrite or nitrate content of wastewater.

Catalytic methods for reducing the nitrite or nitrate content are as described above. European Patent (EP-A) No. 359074 (=USA No. 4990266) Are listed. In that method, the nitrite content and/or nitrate content is They are removed from the water containing them under selective N2 formation. For this purpose, hydrogen is pumped into the water. and then contact the water with the catalyst. This catalyst contains palladium and and/or rhodium or only palladium as noble metal and one metal of the copper group is supported on a porous carrier. This hydrogen is desirably small (with a given amount of oxygen and and the stoichiometrically necessary amount for reducing the nitrite and/or nitrate content. It is pumped into the water in such an amount that it corresponds to at most a 20% excess. Oxygen content of water, nitrous The acid salt or nitrate content may be within a wide range, for example from 0 to 10 ppm (oxygen ), 0-50 ppm+ (nitrite) and 0-500 ppal (nitrate) Vine fluctuates between.

The method is preferably carried out continuously. For this purpose, oxygen, nitrite and/or or nitrite and/or nitrate-containing water with a predetermined content of nitrate at a discharge rate. One gas treatment tank and one reactor each with variable water supply capacity via temperature control pump The water is removed by passing it through one or several reactors containing and gas-treated in the tank with hydrogen gas, optionally under pressure, by the method of the present invention. , intimately mixed and subsequently passed through a reactor containing a catalyst bed with catalyst. desired If the contaminated water is initially introduced into a metering tank and the pH value is adjusted in the tank, If necessary, the pH is adjusted to a value of at most 8 by addition of acid. For sterilization , the water can be passed through a sterilization device, for example a UV radiation lamp, before gas treatment.

Gas treatment and catalytic reactions can be carried out depending on the oxygen and nitrite content of the water and/or It can be repeated as many times as necessary for reduction of nitrate content. to denitrite water , oxygen can be added if desired.

Carrying out this method for removing nitrite and/or nitrate content from water The device comprises a liquid inlet for water and a liquid outlet for water at opposite ends, comprising: a) a) a carrier structure formed from a porous polymer and b) a hydrophobic non-porous polymer. A particularly modular membrane containing layers of one gas treatment tank each having an inlet for water and a water tank connected to the tank; It has a liquid inlet and a liquid outlet for water, possibly with pH measurement and control equipment. each reaction containing a catalyst layer having any of the abovementioned catalysts, It is formed from a vessel. Additionally, the device includes a liquid inlet for introducing water and a with a liquid outlet for drainage and optionally equipped with pH measurement and control equipment. may include a dosing tank. In addition, if desired, sterilization equipment and UV irradiation A tap may also be provided. In addition, arrangements for conveying water into the various equipment parts are provided. There is a duct system. The gas treatment vessel is advantageously arranged adjacent to the reactor. Ma Alternatively, the gas treatment module may be placed directly within the reactor.

The present invention shows that gas treatment with hydrogen using the composite membrane used according to the present invention is In the case of the silicone hose used in Patent Patent (EP-A) No. 359074, It has the great advantage of being 100 times larger. Another advantage is that it dissolves in water. gases that are present can easily permeate through the composite membrane. This makes it possible to increase the amount of hydrogen. A high delivery rate is possible. In addition, hollow fiber membranes are used and the water to be gas treated is In the preferred embodiment of penetrating the membrane, it offers the possibility of adjusting the turbulent flow conditions. do. This results in a particularly high hydrogen excess. The membrane is advantageously very pressure resistant. The equipment costs are low and the space requirements are very small. This makes it very easy It is possible to perform various tasks.

The following section further describes, but does not limit the scope of, the method of the present invention.

Example 1 Hydrogen delivery within the scope of catalytic denitrification 1.1. Membrane used A hollow fiber composite membrane was used. The membrane is manufactured by European Patent (EP-A) No. 29167 No. 9 (US-A No. 4,933,085), polyetherimide (Ulem 100 registered trademark, Manufacturer: General Electric ) and additionally coated on the inner surface with polydimethylsiloxane (VP7660, manufactured by Person: Wacker Chemie.

Munich) was established. The hollow fiber was cut into a length of 33 cm. Its outer diameter is 1. 2 mm, and the inner diameter was 10 mm. When applying pressure shock inside the hollow fiber The bursting pressure is 20 bar, and the bursting pressure when applying a pressure shock from the outside is 7 bar. It was le.

1, 2.1. The inside of the hollow fiber membrane module used is made from polydimethylsiloxane. Example 1.1. The 400 hollow fibers described in were assembled into a module. . The membrane area is 0.415m2.

1, 2.2. Equipment used The equipment is shown in Figure 1 (the equipment for pressure and concentration measurement and the pump are shown in the overview). (Omitted for this reason).

1.2.1. The module 1 with hollow fibers 2 described in It has a supply pipe 3.

The hydrogen tank 4 is a space surrounding the hollow fibers 2 of the module 1 via a valve 5 and a pipe 5. is combined with The tube 6 is connected to the hollow fiber 2 via a header (not shown).

The tube 6 leads into a reactor 7 with a catalyst deposit 8 .

The catalytically treated water can be discharged from the reactor 7 via an outlet pipe 9. catalyst and European Patent (EP-A) Supported contact formed by impregnation with palladium and copper according to the invention of No. 359074 A medium deposition layer was used.

1, 2.3. Implementation of the method The method was implemented for the production of potable water in a water supply facility. Extracted from underground and sewage springs The spring water contained nitrates and had the following analytical data.

pH value Near, 1 Temperature: 10℃ Oxygen content: 3.9 m9 Nitrate content + 52.0 mg/l Nitrite content: <0.01 mg/l Chloride content: 67, Omy/M Sulfate content: 144. Omy/1 Hydrogen carbonate: 262, Om g/total hardness + 26 dH (German hardness) Every time) Salt content: 790 mg/l To improve the solubility of hydrogen, the spring water was brought to a pressure of 4-6 bar. next Water is passed through the hollow fibers of the membrane module under different working conditions, and hydrogen from the cylinder Gas treated without bubbles. The amount of hydrogen fed is orbisfer (0rbis The measurements were carried out continuously using a measuring device manufactured by Phere. water flow rate, water pressure, module pressure drop within the module, flow velocity within the module, volumetric flow of hydrogen, hydrogen pressure and spring water The working conditions, such as the amount of hydrogen dissolved in the water, were measured and summarized in Table 1.

Next, hydrogen-containing water is introduced into the reactor, passed through the catalyst deposit, and treated by the catalyst. did. The nitrate content was reduced by 60-90%. In this example, the method of the present invention is used for a long time. It has been shown that it can be implemented very well over a period of time.

For the experiments listed in Table 1, the hydrogen flow was between 30 and 1001/h (ROTA floating (measured with a body flow meter).

Nitrate content was reduced as listed in Table 1. Dissolved H2 is completely nitric acid It is recognized that it was used for the decomposition of salts and oxygen.

Denitrified, oxygen-free water is passed from a container to a pump in a circulation path to enrich it with oxygen. A module consisting of 8 hollow fibers produced according to Example 1 was passed through. Membrane area was 0.0083 m3. In this case, the water was passed through the internal cavity of the hollow fiber. . Oxygen was strongly introduced to the outside of the hollow fiber. The Reynolds number of water is 3.150. Ta. The pressure at the front of the module is 1.42 bar and at the rear of the module 0.2 bar. It was 9 bar. The water temperature was 20°C. Due to different partial pressures in the gas space Table 2 summarizes the amount of oxygen delivered.

Table 2: Oxygen delivery amount depending on partial pressure Thin ；Hi Agonizing scandal cow 1+ =,, -PCT/EP 92102924 Front page continuation (71) Applicant Gäker SS Folschungszentrum Gösch Tacht Gesellschaft Mituto Beschlenktel Hafrang Federal Republic of Germany D-2054 Gestacht Max Blancouche Trace (no address) Postfach 1160 (72) Inventor: Zell, Michael Elle Federal Republic of Germany D-3150 Paine Wueisdornstrasse 46 (72) Inventor Bischoff, Michael Federal Republic of Germany D-3300 Bra Unschuvaiku Inserval 1 (72) Inventor Mann, Andreas Federal Republic of Germany D-3000 Hanover-1 Freund Allee 1A (72) Inventor Bering, Rolf Dieter Federal Republic of Germany D-2 000 Hamburg 55 Brahmweke 14 (72) Inventor: Peinemann, Klaus Viktor, Federal Republic of Germany D- 2054 Gestacht Belevuberg A (72) Inventor Kneifel, Clemens Federal Republic of Germany D-205 4 Gestacht Surstrasse 10

Claims (8)

[Claims] 1. Injecting hydrogen into an aqueous liquid through a membrane, bubble-free injecting hydrogen into an aqueous liquid a) a carrier structure formed from a porous polymer; and b) a non-porous A membrane containing at least one layer of polymer is used, wherein the aqueous liquid is in an aqueous liquid, characterized in that it is in contact with the membrane on the side of the layer consisting of a non-porous polymer. A method of supplying hydrogen without bubbles to 2. 2. The method according to claim 1, wherein the carrier structure of the membrane has an asymmetric structure. Method. 3. A claim characterized in that the carrier structure of the membrane is formed from polyetherimide. The method according to claim 1 or 2. 4. The non-porous layer may consist of a hydrophobic non-porous polymer, in particular a silicone polymer. 4. A method according to claim 1, characterized in that: 5. Claim 4, characterized in that the non-porous layer has a thickness of 0.1 to 100 μm. How to put it on. 6. characterized in that the membrane is constructed as a flat membrane, a cylindrical membrane or, in particular, as a hollow fiber. 6. A method according to any one of claims 1 to 5. 7. The membrane is configured as a hollow fiber membrane or a tubular membrane, and an additional layer is placed inside the membrane. 5. The method according to claim 4, characterized in that: 8. the aqueous liquid is water containing oxygen, nitrites and/or nitrates; The content of oxygen, nitrite or nitrate in the mixture is catalytically reduced by the injected hydrogen. 2. A method according to claim 1, characterized in that the amount of water is reduced.